Construction Of Bitter Peptide Emulsion System For Bitter Masking And Development Of Microcapsule Products

In the process of forming polypeptides by enzymatic hydrolysis,hydrophobic amino acids are often exposed,which can directly bind to the bitter receptors in the mouth to reflect the bitter taste.These peptides are commonly referred to as bitter peptides.Many protein hydrolysates and peptides showed beneficial physiological functions,such as antioxidant,antibacterial,antihypertensive,hypolipidemic,anti-cancer,anti-diabetes and immune regulation.However,their application as ingredients in functional foods is limited because of their undesirable taste and their tendency to degrade when exposed to gastrointestinal conditions.The objective of this study was to establish whether the sensory perception and gastrointestinal stability of bitter peptides could be improved by encapsulating them within water-in-oil high internal phase emulsions(W/O HIPE).A combination of confocal fluorescence and electron microscopy was used to confirm the formation of W/O HIPEs.The presence of high concentrations of bitter peptides increased the apparent shear viscosity,shear modulus,and sedimentation stability,which was attributed to the apparent viscosity of water phase increased by the introduction of bitter peptides.They also improved the oxidative stability of the HIPEs,which was linked to their antioxidant properties.Electronic-nose and sensory analysis showed that encapsulation of the peptides within the HIPEs substantially reduced their bitterness.Moreover,a simulated gastrointestinal study showed that encapsulation of the peptides in the W/O HIPEs protected them from being released in the stomach.The reduced bitterness and improved gastric retention were attributed to the fact that the peptides were trapped inside the water droplets,which were surrounded by a layer of oil.Our results show that W/O HIPEs can be used to mask the bitterness and improve the gastrointestinal stability of peptides,which may increase their utilization as bioactive ingredients in foods.Secondly,the double emulsion system of bitter peptide was constructed by gelation to investigate the effect of hydrogel position and gel strength on the properties of bitter peptide dual emulsion system.The formation of the double emulsion was determined by a combination of light microscopy and confocal fluorescence microscopy.The hydrogelated double emulsion can successfully encapsulate the bitter peptide,reduce its bitter taste,control its slow release and improve the stability of gastrointestinal digestion.These results are attributed to the fact that bitter peptides are located in the aqueous phase of the double emulsion and the lipid layer in the middle blocks their direct contact with the gastric juice and taste buds.The double emulsion of bitter peptides with inner water gelated had higher encapsulation efficiency.The bitter peptide double emulsion of external aqueous gel had better physical stability.The double emulsion samples with both internal and external aqueous gel showed high encapsulation efficiency and good physical stability.This may be attributed to the addition of gel material in the aqueous phase,which improved the viscosity of the emulsion system,limited the droplet movement,and increased its anti-gravity separation stability.In addition,the bitter peptide double emulsion samples with the water phase gelated can better achieve slow and continuous release.Therefore,the double emulsion of bitter peptide with gelation of both internal and external water phases may be another effective strategy to conceal its bad flavor and improve its long-term stabilityFinally,based on the double emulsion carried of bitter peptides,the combination of maltodextrin,syrup,gelatin and other materials as the wall material,the double emulsion microcapsule encapsulated with bitter peptide was prepared by spray drying.The bitter masking solid powder products was developed.The results showed that the surface of microcapsule powder was smooth,the surface area was 0.155 m~2/g,the pore volume was 0.002 cm~3/g,the pore size was 21.121 nm,the water content was 3.67%,the fat content was 22.7%,the protein content was 15.64±0.13%,the bitter peptide content was 10.34±0.24%.It showed good rehydration and good oxidation stability during storage.The recovered emulsion still had the structure of double emulsion and good physical stability.The sensory evaluation results also showed that the double emulsion microcapsule encapsulated bitter peptides could effectively mask the bad flavor of bitter peptides.These results indicate that double emulsion microcapsules could be used as a new product to encapsulate and deliver flavor substances,mask their undesirable flavors,and expand the application of substances containing undesirable flavors.